Waveguides



Oct. 15, 1963 A. w. GENT ETAL. 3,106,768

WAVEGUIDES Filed Dec. 8, 1959 2 Sheets-sheet l Q A 4/ F/ G. SE

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IN VENTORS: ALFRED W. GENT CHARLES C. EAGLESFIELD RALPH THOMAS LAWRENCE LESLIE CRAMPTON c 1963 A. w. GENT ETAL 3,106,768

WAVEGUIDES Filed Dec.- a, 1959 2 sheets-sheet:

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ALFRED W. GENT CHARLES C. EAGLESFIELD RALPH THOMAS LAWRENCE LESLIE CRAMPTON United States Patent Office 3,106,768 WAVEGUIDES Alfred Walter Gent, Charles tCecil Eaglesiield, Ralph Thomas Lawrence, and Lesiie Crampton, Aldwyeh,

London, England, assignors to International Standard Electric Corporation, New York,

Fiied Dec. 8, 1959, Ser. No. 853,144, Claims priority, application Great Britain Dec. 19, 1.95%

. 6 Ciaims. (Cl. 29--l55.5)

This invention relates to long haul electrical waveguides intended for the transmission of intelligence at high frequencies in the H mode and has particular reference to improve methods of making joints between successive lengths of the helically wound circular waveguide described in British Patent No. 780,503 of L. Lewin et 211., issued November 27, 1957.

In the specification accompanying Belgian Patent No. 580,712 of A. E. Karbowiak issued Ianuary 15, 1960 there is described a method for the manufacture of a circular waveguide such as is described in British Patent No. 780,503 and in the specification accompanying Belgian Patent No. 565,476 of A. W. Gent et al. issued September 8, 1958 there is described another method for the manufacture of such a waveguide.

Both these last mentioned specifications describe methods of manufacturing waveguide of the kind which consists of a cylindrical tubular structure formed by winding a length of insulated wire of circular cross-section to produce a helix with the successive turns in peripheral contact, and in both specifications there is also described a structure comprising an inner helix formed as described above with an outer supporting helix superimposed on the inner helix.

In either the single helix or double helix form adjacent turns are bonded together by a hard setting cement such as one of the epoxy resins to form a rigid tube.

The problem with which the present specification is concerned is the making of joints between successive lengths of helically wound waveguide. By whatever process helically wound waveguides are produced it will be necessary to make joints between successive lengths.

An essential requirement in a joint connecting together two lengths of circular waveguide is that the inner surface of the conducting layer of the waveguide shall be as nearly as possible continuous over the joint.

The present invention is directed to a method of making joints between successive lengths of circular waveguide in such manner that the joints do not lead to reflections. This is no easy problem and extreme accuracy in connecting the tubes together is essential.

According to the invention the jointing of two helical waveguides comprises the steps of trimming the ends of the waveguides, of aligning the ends and of jointing them.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates the trimming of the ends of the waveguides.

FIGURE 2 shows an end of a length of a waveguide prepared for jointing by an external sleeve.

FIG. 3 shows the jointing of two helical waveguides by a fillet of cement. 1

FIGS. 4, 5, 6, and 7 show alternative methods of jointing sleeve terminated helical waveguides.

A preferred method of trimming the ends is shown in FIG. 1 in which the face of the waveguide is cut along a helical surface separating two adjacent turns of the same pitch as the helix. This cut extends over one complete turn of the helix and terminates in a cut through the wire at right angles to its axis. This operation is performed by means of a milling cutter which is carried on a rotating shaft parallel to the axis of the waveguide. The cutter width is not less than the width of the helix wire. By rotating the guide on its axis through at least one. complete revolution and advancing it sirnultaneously along its axis by an amount corresponding to the pitch of the helix a cut of the required shape is generated. Similar results can of course be obtained with a stationary waveguide if the milling device is made to follow a helical path.

The two ends of adjacent helices are then oriented as shown in FIG. 1 so that the cut ends of the wires are placed in close juxtaposition.

Since the ends of the waveguide are liable to be damaged it has been found expedient to provide the ends of the Waveguides with metal sleeve terminations as shown in FIG. 2. In this figure the end 1 of the helically wound waveguide consists of an inner waveguide helix 2 of conducting material surrounded and supported by an outer helix 3 which is normally but not essentially made of wire of the same material as the inner helix, but which could be of any other material including an insulating material, provided it can be produced in wire form and wound to form a helix. It will be seen that the outer helix 3 is terminated a few turns short of the termination of the inner helix 2. A metal sleeve 4 with a stepped inner surface is then slipped over the end of the waveguide and attached to itby means of a suitable: cement. The outer step 5 engages the end of the sup- I porting helix 3'.

In the design according to FIG. 2 the discontinuity between the two waveguides is reduced to a minimum by inserting the waveguide into the sleeve so that the end of the waveguide is flush with the face of the sleeve.

ter attaching the waveguide to the sleeve the face of the latter and the waveguide helix are machined by means similar to those described in connection with FIG. 1 to produce a stepped helical mating surface.

:The trimmed ends of the waveguides can be jointed by means of a suitable cement. If the cement is applied to the trimmed faces of the Waveguides and the faces are pressed together, some cement will be squeezed into the interior of the waveguide where its presence would be harmful. This difiiculty is overcome in the preferred arrangement shown in FIG. 3. In this the ends of two helically wound waveguides as described in British Patout No. 780,503 are shown- The wire helices 9 and 10 forming the waveguides to be jointed are embedded in an insulating compound as shown at 11 and 12. The faces of the two waveguides are machined as wasdescribed in connection with FIG. 1 i.e. helically except that a milling cutter of slightly different shape is used which gives a slight outward chamfer to the face of the waveguide. When the faces of the two waveguides are lined up and clamped together there remains a circumferential V groove 13 which is filled with an adhesive cement.

Waveguides terminated with metal sleeves in accordance with FIG. 2 can be joined in an exactly similar way if the sleeves are provided with chamfered mating surfaces. In general however sleeve terminated waveguides will be jointed together by other means, some of which are shown in FIGS. 4 to 7 in which only half of each joint is shown. In the design of FIG. 4 the two terminating rings 14 and 15 of the helical waveguides 16 and 17 are jointed by means of a third ring 18 which is cemented to rings 14 and 15.

Joints between waveguide runs obtained by means of adhesive cement cannot be taken apart. In applications where it should be possible to break the joint, mechanical. V

couplings can 'be used. FIG. 5 shows the use of sleeves 19 and 26 provided with flanges Z1 and 22'. The flanges Fatented Get. 15, 1963 are bolted together as shown at 23. The coaxiality of the joint is ensured by the shoulder 24. If required a gasket 25 can be inserted as shown.

In the design of FIG. 6 the ring 26 is provided with an external screw thread 27 which is engaged by two internally threaded collars 28. These collars clamp together sleeves 29 and 3G and ensure the continuity of the internal waveguide boundary surface.

In FIG. 7 the ring 31 supports a number of clip members 32 arranged circumferentially, of which only one is shown, which engage with the specially shaped sleeves 33 and 34.

In all the embodiments illustrated in FIGS. 4, 5, 6, and 7 the mating surfaces of the sleeves have preferably helical shape as shown in FIG. 2.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

I. A method of joining two helically wound circular waveguides comprising the steps of exposing the end surfaces to be joined by cutting the waveguides along helical lines of the same pitch as the helices of the waveguides with a milling cutter having a cylindrical cutting face which has a width at least equal to the diameter of the wires used to form the helices whereby the wires forming the helices are cut at substantially right angles to their longitudinal axes, axially aligning the waveguides to be joined, rotating the guides till the surfaces of the cut wires are adjacent one another and mechanically joining the two helical Waveguides to form a substantially continuous waveguide with minimum axial and circumferential gaps between the joined faces.

2. A method of joining two helically wound circular Waveguides having helically wound circular outer coverings which are wound from wire of the same diameter as the wire used to form the waveguides, arranged in the grooves formed by the waveguide helices, and terminated a few turns short of the ends of the Waveguides; and sleeves each of which is shaped to fit around the exposed turns of the waveguide at one end of each waveguide and the end turns of the outer covering adjacent thereto comprising the steps of exposing the end surfaces to be joined by cutting the waveguides along helical lines of the same pitch as the helices of the waveguides with a milling cutter having a cylindrical cutting face which has a width at least equal to the diameter of the wires used to form the helices whereby the wires forming the helices are cut at substantially right angles to their longitudinal axes, axially aligning the waveguides to be joined, rotating the guides till the surfaces of the cut wires are a jacent one another, mechanically joining the two helical waveguides to form a substantially continuous waveguide with minimum axial and circumferential gaps between the joined faces and terminating the outer covering of the waveguides at the ends thereof by slipping a sleeve over each waveguide till it abuts the outer covering and joining the two sleeves. v

3. A method as claimed in claim 2 further comprising cementing each sleeve to its helical waveguide.

4. A method as claimed in claim 3 further comprising cutting the abutting faces of the sleeves along a helical line of the same pitch as the helix of the waveguide.

5. A method as claimed in claim 2 further comprising cementing a ring sleeve to the joined sleeves.

6. A method as claimed in claim 2 further comprising bolting the sleeves together by means of a flange on each sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 2,610,078 Risley et a1. Sept. 9, 1952 

1. A METHOD OF JOINING TWO HELICALLY WOUND CIRCURLAR WAVEGUIDES COMPRISING THE STEPS OF EXPOSING THE END SURFACES TO BE JOINED BY CUTTING THE WAVEGUIDES ALONG HELICAL LINES OF THE SAME PITCH AS THE HELICES OF THE WAVEGUIDES WITH A MILLING CUTTER HAVING A CYLINDRICAL CUTTING FACE WHICH HAS A WIDTH AT LEAST EQUAL TO THE DIAMETER OF THE WIRES USED TO FORM THE HELICES WHEREBY THE WIRES FORMING THE HELICES ARE CUT A SUBSTANTIALLY RIGHT ANGLES TO THEIR LONGITUDINAL AXES, AXIALLY ALIGNING THE WAVEGUIDES TO BE JOINED, ROTATING THE GUIDES TILL THE SURFACES OF THE CUT WIRES ARE ADJACENT ONE ANOTHER AND MECHANICALLY JOINING THE TWO HELICAL WAVEGUIDES TO FORM A SUBSTANTIALLY CONTINUOUS WAVEGUIDE WITH MINIMUM AXIAL AND CIRCUMFERENTIAL GAPS BETWEEN THE JOINED FACES. 